Interpretive Summary: Anaplasmosis is an economically important tick transmitted pathogen of cattle in the United States and other locations where the appropriate tick vectors are located. Due to the ability of Anaplasma marginale to escape immune responses in infected cattle, persistently infected cattle are a reservoir for tick transmission for life. The ability of A. marginale to persist in cattle is one reason for the difficulties in developing a safe and efficacious vaccine. The complete genome sequencing of A. marginale subsp. centrale (a strain used as a live vaccine in some countries, but not the U. S.) allowed for genomic comparisons with other strains and the identification of components of A. marginale for testing as vaccine candidates.

Technical Abstract:
Anaplasma marginale subsp. centrale is a naturally attenuated subtype that has been used as a vaccine for a century. We sequenced the genome of this organism and compared it to those of virulent senso stricto A. marginale strains. The comparison markedly narrows the number of outer membrane protein candidates for development of a safer inactivated vaccine and provides insight into the diversity among strains of senso lato A. marginale.